title: Magnetic relaxation switch and colorimetric detection of thrombin using aptamer-functionalized gold-coated iron oxide nanoparticles.
abstract: We describe a sensitive biosensing system combining magnetic relaxation switch diagnosis and colorimetric detection of human α-thrombin, based on the aptamer-protein interaction induced aggregation of Fe(3)O(4)@Au nanoparticles. To demonstrate the concept, gold-coated iron oxide nanoparticle was synthesized by iterative reduction of HAuCl(4) onto the dextran-coated Fe(3)O(4) nanoparticles. The resulting core-shell structure had a flowerlike shape with pretty narrow size distribution (referred to as "nanorose"). The two aptamers corresponding to human α-thrombin were conjugated separately to two distinct nanorose populations. Once a solution containing human α-thrombin was introduced, the nanoroses switched from a well dispersed state to an aggregated one, leading to a change in the spin-spin relaxation time (T(2)) as well as the UV-Vis absorption spectra of the solution. Thus the qualitative and quantitative detection method for human α-thrombin was established. The dual-mode detection is clearly advantageous in obtaining a more reliable result; the detection range is widened as well. By using the dual-mode detection method, a detectable T(2) change is observed with 1.0 nM human α-thrombin, and the detection range is from 1.6 nM to 30.4 nM.
authors.affiliation: Department of Chemistry, Institute of Biomedical Sciences, Fudan University, Shanghai, PR China.
authors.forename: Guohai
authors.initials: G
authors.lastname: Liang
authors.forename: Shaoyu
authors.initials: S
authors.lastname: Cai
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Youyuan
authors.initials: Y
authors.lastname: Peng
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.forename: Jilie
authors.initials: J
authors.lastname: Kong
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods; D003124:Colorimetry / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006801:Humans; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D013917:Thrombin / Q000032:analysis*
chemical_list: D052157:Aptamers, Nucleotide; D005290:Ferric Compounds; C081676:thrombin aptamer; C000499:ferric oxide; D006046:Gold; D013917:Thrombin